PCBs are often employed to carry multiple integrated circuits which are configured to do a particular function. For example, an array of memory integrated circuits, such as DRAMs, may be arranged on a PCB board to form a single in-line memory module (SIMM). The SIMM may then be inserted into a mother board of a personal computer to significantly expand memory capacity.
A constant goal in designing integrated circuit modules is to pack more integrated circuitry into the same or less space. This may be accomplished by physically scaling down the electrical components employed in the integrated circuits, such as decreasing the transistor gate size at the substrate level. Alternatively, printed circuit boards may be designed to carry more integrated circuits. With present PCB technology, integrated circuits may be mounted on both surfaces of the printed circuit board using through-hole or surface mount techniques. Unfortunately, the PCBs generally cannot be increased in length or height due to space limitations imposed by available areas on mother boards and within computer housings. Accordingly, mounting more integrated circuits onto the same PCB is increasingly more difficult since the external dimensions of the PCB (i.e., height and length) cannot be signicantly changed. Therefore, a need arises for new techniques to pack more integrated circuitry into the same area that is now occupied by double-sided PCBs.
Prior art PCBs have a standard thickness of 0.05 inch. A recent advancement in PCB technology has permitted the thickness of a PCB to be substantially reduced. At this writing, PCBs can be formed with a thickness of approximately 0.016 inch.
An advantage of the present invention is to design a novel stacking arrangement of printed circuit boards by incorporating the thinner PCB technology. The stacking arrangement permits a greater packing density of the integrated circuits into the same space occupied by conventional double sided PCBs. The stacked printed circuit board of the present invention allows a four-fold increase in memory density over prior art double sided memory PCBs, such as a prior art single in-line memory module (SIMM) board.